Thiamine (also spelled "thiamin") is a vitamin, formerly known as vitamin B1. Thiamine was one of the first compounds recognized as a vitamin.

Thiamine is involved in many body functions, including nervous system and muscle function, the flow of electrolytes in and out of nerve and muscle cells, digestion, and carbohydrate metabolism. Very little thiamine is stored in the body and depletion can occur within 14 days. Severe thiamine deficiency may lead to serious complications involving the nervous system, brain, muscles, heart, and stomach and intestines.

Thiamine is used as part of a treatment for metabolic disorders and thiamine deficiency symptoms, as well as in alcoholics. It has been studied for other uses, but conclusions are lacking at this time.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Humans depend on diet for their thiamine needs. Very little thiamine is stored in the body and depletion can occur within 14 days. Severe thiamine deficiency may lead to serious complications involving the nervous system, brain, muscles, heart, and stomach and intestines. Thiamine deficiency can be associated with alcoholism, poor nutrition, cancer, vomiting associated with pregnancy, bariatric surgery, and hemodialysis. Some people may be more at risk of thiamine deficiency. Those with thiamine deficiency or related conditions should receive supplemental thiamine under medical supervision.

A

Alcoholics or those experiencing alcohol withdrawal are at risk of thiamine deficiency and its associated complications. Thiamine has been injected into the vein with other nutrients. Further research is needed on the impact of thiamine on alcoholism.

B

Thiamine has been added to total parenteral nutrition (TPN, nutrition given through the veins) for people who cannot receive thiamine by mouth, such as a multivitamin.

B

Thiamine deficiency can result in a form of dementia. The relationship of thiamine to Alzheimer's disease and other forms of dementia has been studied. However, there is still controversy over whether thiamine supplementation may benefit people with Alzheimer's disease. More research is needed before a firm conclusion can be made.

C

Thiamine-responsive megablastic anemia (TRMA) is a genetic disorder that affects thiamine transport and conversion in the body. Thiamine has been studied for heart problems associated with TRMA, as well as other TRMA symptoms. More information is needed in this area.

C

Active people who reduce food intake may have a higher risk of vitamin deficiency, including thiamine deficiency. More research is needed in this area.

C

B vitamins have been studied for the treatment of clots in blood vessels. Further research is needed in order to form conclusions.

C

Thiamine deficiency has been seen in some people with cancer, possibly due to medication use or poor nutrition. Currently, it remains unclear whether thiamine supplementation may benefit any particular types of cancer. Supplementation may be needed in people with cancer who have or are at risk of thiamine deficiency.

C

Early evidence suggests that high dietary thiamine intake may help reduce the risk of cataracts. Further study is needed before a firm conclusion can be made.

C

Early research suggests that thiamine supplementation may benefit people with cerebellar ataxia after an illness involving fever. Further research is needed.

C

Blood sugar imbalances may increase the risk of clogged arteries. Thiamine has been studied as a way to help widen narrowed arteries. Regular thiamine intake may improve blood vessel function and slow the progression of clogged arteries in people with blood sugar imbalances. Further study is needed.

C

Thiamine is often recommended in people with coma or hypothermia (dangerously low body temperature) of unknown origin. Thiamine has been studied in people with reduced consciousness due to poisoning. More research is needed.

C

Low thiamine levels have been reported in people with Crohn's disease (a form of inflammatory bowel disease). It is not clear whether regular thiamine intake may benefit people with this disease in general.

C

Thiamine has been studied for complications associated with diabetes, involving the nervous system, eyes, blood vessels, and kidneys. Thiamine may improve complications such as increased urination, high levels of glucose in the urine, and high blood cholesterol levels. Regular thiamine intake may also help slow the progression of clogged arteries in some diabetics. More research is needed in this field.

C

Early research suggests that thiamine may improve attention and mental function in people who have epilepsy. Further research is needed.

C

Long-term thiamine deficiency may cause heart failure, which requires thiamine supplementation. It is unclear whether thiamine supplementation may benefit people who have heart failure due to other causes. However, it is reasonable for those with heart failure to take a daily multivitamin including thiamine. More evidence is needed before a firm conclusion can be made.

C

Vitamin deficiency, including thiamine deficiency, has been linked to long-term kidney dysfunction. Taking a multivitamin is often suggested. However, further research is needed in this field.

C

Vitamin B supplements have been used to treat leg cramps during pregnancy. However, more studies are needed to determine if this is effective.

C

Early evidence suggests that thiamine may be effective for menstrual cramps. Further research is needed to confirm these results.

C

Thiamine has been studied as a treatment for mitochondrial disorders, which occur when there are defects in the mitochondria (a part of the cell that produces energy). More research is needed before conclusions can be made.

C

PDH is a disorder caused by the buildup of lactic acid, which may be life-threatening and cause nervous system problems. Early evidence suggests that thiamine supplementation may benefit children with PDH. Further evidence is needed before a firm conclusion can be reached.

C

Early evidence suggests that B vitamins may reduce pain. Further research is needed to determine the effectiveness of thiamine in rheumatism and related disorders.

C

TMJ is a disorder of the chewing muscles and joints. A combination of indomethacin and thiamine has been studied for this condition, but was found to be less effective than acupuncture. More research is needed in this field.

C

Thiamine levels may be lower in elderly people, although there is typically a lack of symptoms. There is limited evidence that thiamine supplementation may benefit people who have low thiamine blood levels. However, general multivitamin use has been suggested in elderly people. More research is needed before a firm conclusion can be made.

C

Early evidence shows that thiamine lacks benefit for hip fractures. However, research is limited and further study is needed.

D

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

The following doses are the U.S. recommended daily allowance (RDA) of thiamine taken by mouth: in adults 19 and older, 1.2 milligrams for males and 1.1 milligrams for females; and in pregnant or breastfeeding women of any age, 1.4 milligrams. Doses of 1-2 milligrams have been taken by mouth daily as a dietary supplement in adults. In people who have or are at risk of thiamine deficiency, 50 milligrams of thiamine have been taken by mouth daily, and doses of 50-100 milligrams of thiamine have been injected into the vein 3-4 times daily.

For Alzheimer's disease, 3 milligrams of thiamine has been taken by mouth daily in three divided doses for up to one year.

For menstrual cramps, 100 milligrams of thiamine has been taken by mouth daily for three months.

For epilepsy, 50 milligrams of thiamine has been taken by mouth daily for six months.

For alcohol withdrawal, 100 milligrams of thiamine hydrochloride has been injected into the muscle or vein.

For alcohol liver disease, 100 milligrams of thiamine has been injected into the vein.

For coma or hypothermia (dangerously low body temperature) of unknown origin, 100 milligrams of thiamine has been injected into the muscle or vein.

For thiamine deficiency caused by nutrition delivered through the vein, 100 milligrams of thiamine has been injected into the vein.

For Wernicke-Korsakoff syndrome (a brain disorder caused by thiamine deficiency), 5-200 milligrams of thiamine have been injected into the muscle or vein, sometimes in divided doses for over two days, or at least 100 milligrams of thiamine has been injected into the vein or muscle.

Children (younger than 18 years)

The following doses of thiamine taken by mouth are considered to be adequate intake (AI): 0.2 milligrams in infants 0-6 months old; 0.3 milligrams in infants 7-12 months old; 0.5 milligrams in children 1-3 years old; 0.6 milligrams in children 4-8 years old; 0.9 milligrams in children 9-13 years old; 1.2 milligrams in males 14-18 years old; and 1 milligram in females 14-18 years old. The RDA for pregnant or breastfeeding women of any age is 1.4 milligrams daily.

Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid in people with a known allergy or sensitivity to any parts in thiamine supplements. Rare, life-threatening allergic reactions have been reported after multiple doses of thiamine injected into the vein, muscle, or skin.

Side Effects and Warnings

Thiamine is likely safe when taken by mouth daily in amounts considered to be RDA: in adults 19 and older, 1.2 milligrams for males and 1.1 milligrams for females; and in pregnant or breastfeeding women of any age, 1.4 milligrams. Thiamine is likely safe in adults as a supplement when taken by mouth daily in doses of 1-2 milligrams. Thiamine is likely safe in people with or at risk of thiamine deficiency, in doses of 50 milligrams taken by mouth daily. The following doses of thiamine are likely safe in children when taken by mouth daily: 0.2 milligrams in infants 0-6 months old; 0.3 milligrams in infants 7-12 months old; 0.5 milligrams in children 1-3 years old; 0.6 milligrams in children 4-8 years old; 0.9 milligrams in children 9-13 years old; 1.2 milligrams in males 14-18 years old; and 1 milligram in females 14-18 years old.

The following doses of thiamine are considered to be possibly safe: 50-100 milligrams taken by mouth daily for 3-6 months; 50-100 milligrams injected into the vein 3-4 times daily; and 5-200 milligrams injected into the muscle in five divided doses over two days.

Thiamine may cause low blood pressure. Caution is advised in people who have low blood pressure or those taking drugs that lower blood pressure.

Caution is advised in people with diabetes or high blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar or that widen blood vessels.

Use cautiously in breastfeeding women, people who have abnormal heart rates, and those receiving chemotherapy.

Avoid high doses of thiamine injected into the vein or brain. Avoid doses higher than those found in marketed products, unless under the advice of a health professional.

Avoid in people with a known allergy or sensitivity to any parts in thiamine supplements.

Avoid using in the absence of vitamin B6 and nicotinamide, as life-threatening brain damage may occur.

Caution is advised when using medications that lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.